Apparatus for controlling the temperature of blood during extracorporeal circulation



Nov. 20, 1962 R. L. FUSON 3,064,649

APPARATUS FOR CONTROLLING THE TEMPERATURE OF BLOOD DURING EXTRACORPOREAL CIRCULATION Filed Oct- 1, 1959 3 Sheets-Sheet 1 D Z3 l -iog 15 F 22 Z4 2/ 2b INLETToHEBTEXIHiMER 4 IHHERSION 3 HEBTER.

SUPPLY INVENTOR. Eaaeer L. fuse/v.

- firrok/vfir-f.

R. L. FUSON TROLLI Nov. 20, 1962 3,064 LOOD APPARATUS FOR CON NG THE TEMPERATURE OF B DURING EXTRACORPOREAL CIRCULATION 3 Sheets-Sheet 2 Filed 001.- l, 1959 INVENTOR. F0552? A. FZ/a'oM Nov. 20, 1962 3,064,649

R. L. F USON APPARATUS FOR CONTROLLING THE TEMPERATURE OF BLOOD DURING EXTRACORPOREAL CIRCULATION Filed Oct. 1, 1959 3 Sheets-Sheet 3 r O A INVENTOR. Rae's/er L F050.

3,fi64,549 Patented Nov. 20, 1952 tion Filed Oct. 1, 1959, Ser. No. 843,742 Claims. (Cl. 128-214) This invention relates generally to extracorporeal circulation of blood and in particular to apparatus for inducing hypothermia or hyperthermia or maintenance of normothermia in living organs or tissue during extracorporeal circulation.

One of the factors responsible for the recent progress in intracardiac surgery has been the use of hypothermia which protects the cardiac and cerebral tissues during the period of reduced circulation. It has been found that much higher recovery rates can be attained when using hypothermia in conjunction with low extracorporeal blood flows as opposed to normothermia. It is now generally recognized that hypothermia and extracorporeal circulation complement each other in open heart surgery.

Until recently all clinical hypothermia has been induced externally, that is, by packing the anesthetized patient in an ice pack. Following the surgical procedure, the patient, in this process, is returned to normothermia by the application of hot packs, hot water bottles or the like. Since it takes two to three hours to cool and three to four hours to rewarm the patient, a very long period ofanesthesia is required. A further defect in this process is that it may produce surface cooling shock or frostbite. In general, this process for externally producing hypothermia is cumbersome, time consuming, and prolongs the anesthetic period.

Since the external method of producing hypothermia involves rather difificult problems, both practical and physiological, a process for inducing hypothermia by internal heat exchange has distinct advantages. Such internal heat exchange can be accomplished by altering the temperature of the infused blood duringextracorporeal circulation. The present invention is directed to an apparatus and process for accomplishing heat exchange in the blood during extracorporeal circulation.

The primary object of the present invention is to providean. apparatus for use in conjunction with extracorporeal blood circulation apparatus which permits accurate control of the blood. temperature, and hence,v body or organ temperature.

A further object of the present invention is to provide an efiicient heat exchange apparatusfor, fixing the temperature of blood circulated extracorporeally.

A fnrther object of the present invention is to provide an apparatus of the type referred to which functions to evacuate any bubbles and tofilter any clots or other embolic type matter from the circulating blood.

Afurther object of the present invention is toprovide an apparatus of the type referred to which can be easily and rapidly disassembled for cleaning.

A further object of the present invention is to provide an apparatus of the type referred to which, by utilizing alternate component parts can be readily changed with regard to its heat exchange and priming volume capacity.

Afurther object of the present invention is to provide a process for lowering the temperature of living organs or parts of a body to a value such that the blood supply to the organ can be temporarily suspended thereby permitting operations on the organ in a bloodless field without damage to the organ.

These and other objects will become apparent as'the description proceeds with reference to the accompanying drawings in which:

F18. 1 is a diagrammatic view of the apparatus of the present invention incorporated into a system for providing extracorporeal circulation.

FIG. 2 is a perspective view of the apparatus mounted within a cabinet.

FIG. 3 is a side view, partially in section, of the heat exchange assembly.

PEG. 4 is a side sectional view of the filter assembly.

FIG. 5 is a side view, partially in section, of the heat exchange assembly when modified to provide a lower vol- LL; etric capacity.

PEG. 6 is a side view of a mounting stand for the heat exchange assembly and the filter assembly.

Referring initially to FIGS. 1 and 2, the tube ill conducts blood from a conventional oxygenator which receives blood from a patient undergoing extracor-poreal circulation. From the tube it the blood is introduced into the heat exchange assembly of the present invention indicated generally at 11. Tube 12 conducts blood from the heat exchange assembly into the filter assembly indicated generally at 13. A tube 14 conducts blood from the outlet of the filter assembly to the femoral or other convenient systemic artery of the patient.

The remaining portions of the system shown in FIG. 1 are utilized to provide a heat exchange fluid, at a controlled temperature for the heat exchange assembly. This apparatus includes a conventional motor driven pump 16 which draws a heat exchange fluid, such as ethylene glycol, from a supply or receiver tank 17. The pump supplies fiuid to a conventional refrigeration unit indicated at 18' and to a conventional heating unit 19; The heating unit may take the form of an electrical immersion heater. A constant supply of both cooled and heated fluid is thus supplied to the three-way mixing valve indicated schematically at 21. The mixing valve is of the conventional type, operated by an actuating motor 22 through a suitable linkage. The operation of the actuating motor is controlled by a conventional bridge-type indicating temperature controller 23. A thermocouple 24, extending into the filter assembly 13 senses the temperature of the blood flowing from the filter assembly and, through the controller 23, causes the motor 22 to position the valve 21 so as to maintain the blood flowing from the filter assembly at a constant temperature, the magnitude of which depends upon the setting of the controller. It will be understood that the temperature sensing element, such as a thermocouple might, alternatively, be placed so as to directly sense body temperature. Various hand valves 26 and by-pass lines add to the flexibility of the system and permit flushing or cleaning. Check valves 27 effectively isolate the cooling unit 18 and the heating unit 19.

As may be seen in FIG. 2, the components just described may be mounted within a cabinet of the type indicated at 28, having a control panel 29. At one end of the cabinet, the heat exchange assembly 11 and the filter assembly 13 may be suitably supported on a vertical post 31.

Referring now to FIG. 3, the heat exchange assembly will be described in detail. The assembly includes a tubular housing 32 which at its lower end carries a header plate 33. The header plate is provided'with circularly arranged series of apertures, the outer apertures being indicated at 34, the next inwardly adjacent series of apertures being indicated at 36, the next inwardly adjacent series of apertures being indicated at 37, and the central aperture being indicated at 38. At its upper end, the housing 32 carries an upper header plate 39 Which is also provided with a series of circularly arranged series of apertures aligned with the apertures Tat-38 of the lower header plate. Extending between the header plate apertures are a series of tubes indicated at 41, with the central tube, whose axis coincides with the axis of the hous ing, being indicated at 41a. Adjacent its base, the housing 32 is rigidly attached to an annular member 42 which is externally threaded.

Threaded upon the annular member 42 is a lower cap 43; a silicone rubber -ring 44 serves to seal the cap to the annular member 42. The external vertical surface of the cap 43 is knurled as indicated at 46 to facilitate assembly and removal of the cap on the housing. The inner face of the cap member is formed so as to present a convex conical surface 47 to the lower header plate 33, the apex of the conical surface being vertically aligned with the axis of the center tube 41a.

' The cap is further provided with a blood inlet aperture indicated at 48, the aperture communicating with a fitting 49 to which may be attached the tube It) referred to in FIG. 1. As may be seen in FIG. 3, the blood inlet aperture is positioned so that its axis extends generally tangentially to the base of the conical surface 47.

The upper end of the housing 32 is rigidly received within an annular member 51 which is externally threaded to receive the correspondingly threaded marginal portion of an upper cap 52. An O-ring 53 serves to seal the cap 52 to the annular member. The exterior vertical surface of the cap 52 is knurled as indicated at 54 to facilitate assembly and disassembly of the heat exchange apparatus. The upper cap is formed to provide a generally concave conical surface 56 to the upper header plate 39 and is provided with a blood outlet aperture 57 at the apex of the conical surface. The portion of the cap adjacent the outlet aperture is extended to provide a tube or fitting 58 to which may be attached the tube 12 referred to in describing FIG. 1.

Extending from one sideof the housing 32 is a threaded fitting 59 which communicates with the interior of the housing and provides an inlet for the heat exchange fluid proceeding from the three-way valve 21 of FIG. 1. Extending from the inner face of the housing are interfitting bafiies 61 which direct the heat exchange fluid in a tortuous path across the tubes 41 for even distribution of the fluid. A fitting 62 provides an outlet passage for the heat exchange fluid after it has moved in heat exchange relation with the tubes, the fitting 62 being connected to the supply tank 17 of FIG. 1.

Referring to FIG. 4, the filter assembly will now be described and includes a cylindrical housing 63. 'The housing 63 is bottomed on the marginal area of a lower end cap 6-4, an O-ring 66 providing a seal therebetween. Extending upwardly from diametrically opposite sides'of the cap 64 are frame members 67 which at their upper ends are rigidly secured to an annular member 68. The annular member is threaded to accommodate an upper cap 69 having a knurled surface 71. A silicone rubber gasket 72 tops the upper end of the housing 63 and a silicone rubber O-ring 73 seals and clamps the marginal portion 74 of a conical, wire mesh filter element '76. The cap 69 presents a concave, generally conical surface 77 to the open end of the filter element, and at the apex of the conical surface 77, there is disposed a manually operable valve 78 connected to a tube 79 which, in turn, may be connected to a point in the blood oxygenating and pumping system (not shown) which is at a reduced pressure. There is thus provided a valved vent at the filter assembly cap.

The lower cap 64 is provided with an inlet aperture through which an inlet tube 81 extends, the tube being sealed within the aperture. The portion of the tube extending exteriorally of the cap 64 is adapted to have fastened thereto the tube 12 (FIG. 1) by means of a quick-disconnect coupling, not shown. Within the filter assembly, the tube, in the area indicated at 82, is provided with an increased diameter so as to diminish the velocity of the incoming blood and facilitate the separation of bubaceaaao 4. .bles or gas entrapments therein. The tube enters the filter element 76 at its apex and extends axially therein to a point adjacent the upper end of the filter element. The cap 64 also carries a fitting 24 (previously mentioned with reference to FIG. 1) which is threaded to accommodate a conventional temperature sensing probe which may include a thermocouple element indicated generally at 84. The temperature sensing probe includes a lead cable 86 which is connected to the controller 23 mentioned with reference to FIG. 1. The lower cap 64 presents a generally concave conical surface 87 to the interior of the filter assembly and is elongated at the apex of the conical surface to provide a tube 83 which may be connected by means of a quick-disconnect fitting or similar means to the tube 14 previously referred to in describing FIG. 1.

In operation, with the pump 16 functioning to drive heat exchange fluid through the heat exchange assembly and with blood flowing through the tube 10, the incom-r ing blood will enter the heat exchange assembly through the aperture 48 and will be directed into the lower cap member 43 in a free vortex path and will rise through the tubes 41 and 41a. Since the pressure will be lowest at the center of the vortex, bubbles or gas entrapments will tend to accumulate in the central tube 41a. The blood will then move through the tube 58, tube 12 and tube 81 into the interior of the filter element 76 in the, filter assembly. As the blood traverses the enlarged portion 82, its velocity will be decreased to facilitate release of bubbles upwardly through the valved vent 78. The blood flowing from the upper end of the tube 81 will move downwardly through the filter element 76 'past the temperature sensing probe 84 and into the tube 88. From the tube 88, the blood is returned through the tube 14 to, for example, the femoral or other convenient systemic artery of the body undergoing extracorporeal circulation. As the blood leaves the filterassembly, its temperature will be sensed by the probe 84 and fed back to the control system for regulating the temperature of the heat exchange fluid moving through the heat exchange assembly.

It should be noted that the heat exchange assembly and the filter assembly can both' be conveniently disassembled and cleaned with a detergent and warm water. The filter element 76 can be used repeatedly when cleaned with trypsin, a detergent and warm water. The filter element 76 is formed of stainless steel mesh and is conical to provide a maximum filtering surface area. The surfaces of the assemblies in contact with circulating blood are preferably treated with a silicone antifoam material. The cylindrical housing 63 is preferably formed of Pyrex. The concave surface 56 of the upper end cap 52 in the heat exchange assembly and the concave surface 87 in the lower cap 64 of the filter assembly prevent the trapping of bubbles within these assemblies.

Referring now to FIG. 5, the central housing 32 of the heat exchange assembly is shown with modified forms of the upper and lower cap members in place thereon. These modified cap members are given the same reference numerals as those in FIG. 3 but with the sutfix a. In both of these modified caps, the cham bers formed therein are of reduced size, the O-rings 44a and 53a serving to seal the caps against the header plates 33 and 39 respectively. The modified caps are used when it 'is desirable to cut down the volumetric capacity of the heat exchange assembly, the capacity of the modified arrangement of FIG. 5 being, for example 300 cc. as compared to 500 cc. for the assembly of FIG. 3. This convenient form for altering the capacity of the heat exchange assembly permits eflicient use of the apparatus on patients of difiering size.

In FIG. 6, there is shown a stand for supporting the heat exchange assembly and filter assembly in vertically aligned relation when they are not mounted upon the cabinet 28 of FIG. 2. The stand includes a base member 91 which has a downaturned abutment 92 and a caster assembly 93. A socket 94 in the base has press fitted therein, a vertical rod 96. The rod accommodates a lower bracket 97 adjustably positionable upon the rod, the bracket being formed so as to support the base of the heat exchange assembly 11. The upper end of the heat exchange assembly is supported by a bracket 98 also adjustably positionable upon the rod 96 and carrying a clamp plate 99 which may be tightened against the upper cap of the heat exchange assembly by means ofthrumb screw 101. 'The upper end of the filter assembly is supported by means of a bracket 162 adjustably positioned on the rod 96 and held thereon by means of a clamp plate 103 and thumb screw 104.

The method of internal heat exchange for the induction of hypothermia, which is facilitated by the apparatus of the' present invention, permits accurate control of the patients temperature throughout surgery. The cooling period is materially shortened and the period of anesthesia can thereby be reduced. The internal heat exchange approach permits the most efiicient cooling of the vital organs which are most susceptible to low blood flows (the brain, heart and kidneys). These organs have the richest blood supply and hence are the tissues most exposed to the cooling inflow of blood. Because the internal heat exchange approach permits accurate control of the temperature of internal organs, hypothermia, itself, may be used as an anesthetic and to produce cardiac arrest in intracardiac surgery. While the apparatus of the present invention has been described herein as useful in producing hypothermia, it will be evident that it may have application to other extracorporeal blood circulation procedures, such as maintaining normothermia or hyperthermia.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being bad to the appended claims.

The invention claimed is:

1. A blood filter and heat exchange apparatus for use with extracorporeal blood circulating apparatus comprising a heat exchange assembly and a filter assembly, means for supporting said filter assembly above and adjacent to said heat exchange assembly, said heat exchange assembly comprising a tubular housing having its axis disposed substantially vertically, a bank of open ended tubes disposed within said housing and supported by an upper header plate and a lower header plate, a cup shaped lower cap member on the lower end of said housing, the inner face of said cap being formed to present a convex conical surface to said lower header plate and having its apex vertically aligned with the axis of said housing, a blood inlet aperture in said lower cap member adapted to receive blood from an extracorporeal circulating apparatus, said blood inlet aperture having its axis extending generally tangentially to the base and circumference of said conical surface whereby blood flowing through said aperture is directed in a free vortex path within said lower cap to establish minimum pressure adjacent the central tubes in said bank for release of bubbles from the blood flowing therein, an upper cap upon the upper end of said housing with a blood outlet aperture therein, said filter assembly comprising a cylindrical housing, a lower end cap for said housing having a blood outlet aperture therein, a conically shaped filter element having its base disposed at the upper end of said housing and extending within the housing coaxially therewith, an upper end cap closing the upper end of said filter housing and having a vent therein, a blood inlet aperture in said lower filter end cap, an inlet tube extending through said aperture and centrally into said filter element, said inlet tube having an increased diameter 6;. at a point adjacent its entry into said filter element whereby the velocity of blood flow is reduced to facilitate the release of any bubbles therein, means for circulating a heat exchange fluid at controlled temperature within said heat exchange housing and in heat exchange relation to said tubes, and means providing communication between said heat exchange assembly blood outlet and said filter assembly blood inlet, whereby blood flowing through said heat exchange tubes is thermally altered and is thereafter filtered in said filter assembly with any bubbles or gas entrapments being released through said filter assembly vent.

2. A blood filtering and heat exchange apparatus for use with extracorporeal blood circulating apparatus comprising a heat exchange assembly and a filter assembly,

means for supporting said filter assembly above and adjacent to said heat exchange assembly, said heat ex change assembly comprising a tubular housing having its axis disposed vertically, a bank of open ended tubes disposed Within said housing and supported by an upper header plate and a lower header plate, a cup-shaped lower cap member on the lower end of said housing, the inner face of said cap being formed to present a convex conical surface to said lower header plate and having its apex vertically aligned with the axis of said housing,

a blood inlet aperture in said lower cap member adapted to receive blood from an extracorporeal circulating apparatus, said blood inlet aperture having its axis extending generally tangentially to the base and circumference of said conical surface whereby blood flowing through said aperture is directed in a free vortex path within said lower cap to establish minimum pressure adjacent the central tubes for release of bubbles from the blood flowing therein, an upper cap upon the upper end of said housing, with a blood outlet aperture therein said filter assembly comprising a tubular housing, a lower end cap for said housing having a blood outlet aperture therein, a conically shaped filter element having its base disposed at the upper end of said housing and extending within the housing coaxially therewith, an upper end cap closing the upper end of said filter housing and having a vent therein, a blood inlet aperture in said lower filter end cap, an inlet tube extending through said aperture and into said filter element, means for circulating a heat exchange fluid at controlled temperature within said heat exchange housing and in heat exchange relation to said tubes, and means providing communication between said heat exchange assembly blood outlet and said filter assembly blood inlet, whereby blood flowing through said heat exchange tubes is thermally altered and is thereafter filtered in said filter assembly with any bubbles or gas entrapments being released through said filter assembly vent.

3. A blood filtering and heat exchange apparatus for use with extracorporeal blood circulating apparatus comprising a heat exchange assembly and a filter assembly, means for supporting said filter assembly above and adjacent to said heat exchange assembly, said heat exchange assembly comprising a tubular housing having its axis disposed substantially vertically, a bank of open ended tubes disposed within said housing and supported by an upper header plate and a lower header plate, a cup-shaped lower cap member on the lower end of said housing, the inner face of said cap being formed to present a convex conical surface to said lower header plate and having its apex vertically aligned with the axis of said housing, a blood inlet aperture in said lower cap member adapted to receive blood from an extracorporeal circulating apparatus, said blood inlet aperture having its axis extending generally tangentially to the base and circumference of said conical surface whereby blood flowing through said aperture is directed in a free vortex path within said lower cap to establish minimum pressure adjacent the central tubes for release of bubbles from the blood flowing therein, an upper cap upon the upper end of said housing with a blood outlet'aperture therein, said filter assembly comprising a tubular housing, a lower end cap for said housing having a blood outlet aperture therein, a filter element disposed within said housing, an upper end cap closing the upper end-of said filter housing and having a vent therein, a blood inlet aperture in said lower filter end cap, an inlet tube extending through said aperture and terminating on the upstream side of said filter element, means for circulating a heat exchange fluid at controlled temperature within said heat exchange housing and in heat exchange relation to said tubes, and means providing communication between said heat exchange assembly blood outlet and said filter assembly blood inlet, whereby blood flowing through said heat exchange tubes is thermally altered and is thereafter filtered in said filter assembley with any bubbles or gas entrapments being released through filter assembly vent.

4. A heat exchanger apparatus for use with extracorporeal blood circulating apparatus comprising a heat exchange assembly comprising a tubular housing having its axis disposed vertically and having a heat exchange fluid inlet aperture adjacent its lower end and a heat exchange fluid outlet aperture adjacent its upper end, a bank of open ended tubes disposed Within said housing and supported by an upper header plate and a lower header plate, said tubes being arrangediin concentric circular series with the center tube having its axis coincident with the axis of the housing, a cup-shaped lower cap member threadedly received on the lower end of said housing, the inner face of said cup being formed to present a convex conical surface to said lower header plate and having its apex vertically aligned with the axis of said center tube, a

blood inlet aperture in the sidewall of said lower cap merit-,-

Within said lower cap to establish minimum pressure at said center tube for release of bubbles from the blood flowing therein, an upper cap threadedly received upon the! upper end of said housing and presenting a generally co ncave conical surface to said upper header plate, and a blood outlet aperture in said uppertcap at the apexof said" conical surface. 7

5. A heat exchange assembly, as claimed in claim 4' in which said upper cap and lower cap member are interchangeable with auxiliary upper cap and lower cap members, and have an annular surface which functions to mask the adjacent ends of the outermost tubes when threaded on said housing to reduce the volumetric capacity" of said assembly. 7

References Cited in the file of thispatent UNITED STATES PATENTS r 2,607,567 Hobbs Aug. l9, 1952" 20 2,659,368 Gibbon et al. Nov. 17, 1953 2,876,769 Cordova Mar. 10, 1959' OTHER REFERENCES Brown et al.: An Efficient Blood HeatExchang er for Use With Extracorporeal Circulationj Surgery, August,

l958, volume 44, No. 2, pages 372-377. 

